• Journal of Microbiology and Biotechnology
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• v.16 no.3
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• pp.391-398
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• 2006

$NF-{\kappa}B$ is a transcription factor involved in the innate immunity against bacterial infection and inflammation. It is also known to render cells resistant to the apoptosis caused by some anticancer drugs. Such a chemoresistance of cancer cells may be related to the activation of $NF-{\kappa}B$ transcription factor; however, the mechanism of activation is not well understood. Here, we demonstrate that a chemotherapeutic agent, etoposide, independently stimulates the $I{\kappa}B{\alpha}$ degradation pathway and PI3-kinase/Akt signaling pathway: The classical $I{\kappa}B{\alpha}$ degradation pathway leads to the nuclear translocation and DNA binding of p65 subunit through $IKK{\beta}$ kinase, whereas the PI3-kinase/Akt pathway plays a distinct role in activating this transcription factor. The PI3-kinase/Akt pathway acts on the p50 subunit of the $NF-{\kappa}B$ transcription factor and enhances the DNA binding affinity of the p50 protein. It may also explain the role of the PI3-kinase/Akt pathway in the anti-apoptotic function of $NF-{\kappa}B$ during chemoresistance of cancer cells.

• Biomedical Science Letters
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• v.13 no.2
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• pp.75-81
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• 2007

Sodium salicylate (NaSal), a chemopreventive drug, has been shown to induce apoptosis and cell circle arrest depending on its concentrations in a variety of cancer cells. In A549 cells, low concentration of NaSal (5$\sim$10 mM) induces cell cycle arrest, whereas it induces apoptosis at higher concentration of 20 mM. In the present study, we examined the molecular mechanism for NaSal-induced cell cycle arrest. NaSal induced expression of p53, p21 (Wafl/Cipl), and p27 (Kipl) that play important roles in cell cycle arrest. p53 induction was mediated by its phosphorylation at Ser-15 that could be prevented by the PI3K-related kinase (ATM, ATR and DNA-PK) inhibitors including wortmannin, caffeine and LY294002. In addition, NaSal-induction of p2l (Wafl/Cipl) was detected in P53 (+/+) wild type A549 cells but not in p53 (-/-) mutant H1299 cells, indicating p53-dependent p21 (Wafl/Cipl) induction. In contrast, p27 (Kipl) that is a negative regulate. of cell cycle with p21 (Wafl/Cipl) was observed both in A549 cells and H1299 cells. Thus, 5 mM NaSal appeared to cause cell cycle arrest through inducing the cyclin-dependent kinase inhibitor p21 (Wafl/Cipl) via PI3K-related protein kinase-dependent p53 activation as well as by up-regulating p27 (Kipl) independently of p53 in A549 cells.

• Archives of Pharmacal Research
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• v.27 no.7
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• pp.757-762
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• 2004

The protective adaptive response to electrophiles and reactive oxygen species is mediated by the induction of phase II detoxifying genes including glutathione S-transferases (GSTs). NF-E2-related factor-2 (Nrf2) phosphorylation by protein kinase C (PKC) is a critical event for its nuclear translocation in response to oxidative stress. Previously, we have shown that peroxynitrite plays a role in activation of Nrf2 and Nrf2 binding to the antioxidant response element (ARE) via the pathway of phosphatidylinositol 3-kinase (PI3-kinase) and that nitric oxide synthase in hepatocytes is required for GSTA2 induction. In view of the importance of PKC and Pl3-kinase in Nrf2-mediated GST induction, we investigated the role of these kinases in peroxynitrite formation for GSTA2 induction by oxidative stress and determined the relationship between PKC and PI3-kinase. Although PKC activation by phorbol 12-myristate-13-acetate (PMA) did not increase the extents of constitutive and inducible GSTA2 expression, either PKC depletion by PMA or PKC inhibition by staurosporine significantly inhibited GSTA2 induction by tert-butylhydroquinone (t-SHa) a prooxidant chemical. Therefore, the basal PKC activity is req- uisite for GSTA2 induction. 3-Morpholinosydnonimine (SIN-1), which decomposes and yields peroxynitrite, induced GSTA2, which was not inhibited by PKC depletion, but slightly enhanced by PKC activation, suggesting that PKC promotes peroxynitrite formation for Nrf2-mediated GSTA2 induction. Treatment of cells with S-nitroso-N-acetyl-penicillamine (SNAP), an exogenous NO donor, in combination with t-BHQ may produce peroxynitrite. GSTA2 induction by SNAP ＋ t-BHQ was not decreased by PKC depletion, but rather enhanced by PKC activation, showing that the activity of PKC might be required for peroxynitrite formation. LY294002 a P13-kinase inhibitor blocked GSTA2 induction by t-BHQ, which was reversed by PMA-induced PKC activation. These results provide evidence that PKC may playa role in formation of peroxynitrite that activates Nrf2 for GSTA2 induction and that PKC may serve an activator for GSTA2 induction downstream of PI3-kinase.

• Journal of Life Science
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• v.32 no.2
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• pp.86-93
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• 2022

Lupeol is a type of pentacyclic triterpene and has been reported to have pharmacological activities against various diseases; however, the effect of lupeol on glucose absorption has not been elucidated yet. This study aimed to investigate the effect of lupeol on glucose uptake in 3T3-L1 adipocytes. Lupeol significantly facilitated glucose uptake by translocating glucose transporter type 4 (GLUT4) to the plasma membrane of the 3T3-L1 adipocytes, which was related to activation of the phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) and 5 'adenosine monophosphate-activated protein kinase (AMPK) pathways. In the PI3K/AKT pathway, lupeol stimulates the phosphorylation of insulin receptor substrate 1 (IRS-1), which activates PI3K. Its activation by lupeol promotes the phosphorylation of AKT, but not the atypical protein kinase C isoforms ζ and λ. Lupeol also promoted the phosphorylation of AMPK. The activation of AMPK increased the expressions of the plasma membrane GLUT4 and the intracellular glucose uptake. The increase in the glucose uptake by lupeol was suppressed by wortmannin (PI3K inhibitor) and compound C (AMPK inhibitor) in the 3T3-L1 adipocytes. The results indicate that lupeol can facilitate glucose uptake by increasing insulin sensitivity through the stimulation of the expression of plasma membrane glucose transporter type 4 via the PI3K/AKT and AMPK pathways in the 3T3-L1 adipocytes.

• Journal of Applied Biological Chemistry
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• v.64 no.4
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• pp.447-451
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• 2021

In this study, we discovered for the first time that linarin, a flavonoid compound, enhances melanin biosynthesis in B16F10 cells, and subsequently elucidated the underlying mechanism of linarin-induced melanogenesis. Linarin showed no cytotoxicity at a concentration of 42 μM and significantly increased intracellular tyrosinase activity and melanin content in B16F10 cells. Mechanistic analysis showed that linarin increased the expression of tyrosinase, tyrosinase-related protein 1 (TRP-1), and microphthalmia-associated transcription factor (MITF) that are related to melanogenesis. Moreover, linarin decreased the phosphorylation of extracellular signal-regulated kinase (ERK) and protein kinase B (AKT). Finally, we evaluated the effect of the structure-activity relationship of linarin and its aglycone on melanogenesis. The results indicated that linarin enhances the expression of melanogenic proteins by activating MITF expression via the modulation of mitogen-activated protein kinase (MAPK), phosphatidylinositol 3-kinase (PI3K), and protein kinase B signaling pathways in B16F10 cells, thereby enhancing melanogenesis.

• Journal of Life Science
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• v.25 no.9
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• pp.976-983
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• 2015

Achyranthoside C dimethyl ester (ACDE) is an oleanolic acid glycoside from Achyranthes japonica which has been used in traditional medicine for the treatment of edema and arthritis. In this study, we investigated the anti-inflammatory effects of ACDE in RAW264.7 macrophages. ACDE significantly induced heme oxygenase-1 (HO-1) gene expression in RAW264.7 cells, while ACDE improved LPS-induced toxicity of cells. And ACDE induced nuclear translocation of nuclear factor E2-related factor 2 (Nrf2), a transcription factor that regulates HO-1 expression. Further study demonstrated that ACDE-induced expression of HO-1 was inhibited by inhibitors of phosphatidylinositol 3-kinase (PI-3K) (LY294002), c-Jun kinase (JNK) (SP600125), extracellular signal regulated kinase (ERK) (PD98059) and p38 kinase (SB203580). Moreover, ACDE phosphorylated Akt, JNK, ERK, and p38 MAPK. In addition, ACDE inhibited LPS-induced NO secretion as well as inducible NO synthase (iNOS) expression in a dose-dependent manner. The inhibitory effects of ACDE on iNOS expression were abrogated by small interfering RNA (siRNA)-mediated knock-down of HO-1. Therefore, these results suggest that ACDE suppresses the production of pro-inflammatory mediator such as NO by inducing HO-1 expression via PI-3K/Akt/MAPK-Nrf2 signaling pathway. These findings could help us to understand the active principle included in the roots of A. japonica and the molecular mechanisms underlying anti-inflammatory action of ACDE.

• The Korean Journal of Pain
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• v.34 no.2
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• pp.176-184
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• 2021

Background: Diabetes-related neuropathic pain frequently occurs, and the underpinning mechanism remains elusive. The periaqueductal gray (PAG) exhibits descending inhibitory effects on central pain transmission. The current work aimed to examine whether inflammatory cytokines regulate mechanical allodynia and thermal hyperalgesia induced by diabetes through the phosphoinositide 3-kinase (PI3K)-mammalian target of rapamycin (mTOR) pathway in the PAG. Methods: Streptozotocin (STZ) was administered intraperitoneally to mimic allodynia and hyperalgesia evoked by diabetes in rats. Behavioral assays were carried out for determining mechanical pain and thermal hypersensitivity. Immunoblot and ELISA were performed to examine PAG protein amounts of interleukin-1β (IL-1β), IL-6, and tumor necrosis factor-α (TNF-α), as well as their corresponding receptors in STZ rats, and the expression of PI3K/protein kinase B (Akt)/mTOR signaling effectors. Results: Increased PAG p-PI3K/p-Akt/p-mTOR protein amounts were observed in STZ-induced animals, a PI3K-mTOR pathway inhibition in the PAG attenuated neuropathic pain responses. Moreover, the PAG concentrations of IL-1β, IL-6, and TNF-α and their receptors (namely, IL-1R, IL-6R, and tumor necrosis factor receptor [TNFR] subtype TNFR1, respectively) were increased in the STZ rats. Additionally, inhibiting IL-1R, IL-6R, and TNFR1 ameliorated mechanical allodynia and thermal hyperalgesia in STZ rats, alongside the downregulation of PI3K-mTOR signaling. Conclusions: Overall, the current study suggests that upregulated proinflammatory cytokines and their receptors in the PAG activate PI3K-mTOR signaling, thereby producing a de-inhibition effect on descending pathways in modulating pain transmission, and eventually contributing to neuropathic pain.

• Molecules and Cells
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• v.40 no.5
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• pp.315-321
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• 2017

The inositol polyphosphates are a group of multifunctional signaling metabolites whose synthesis is catalyzed by a family of inositol kinases that are evolutionarily conserved from yeast to humans. Inositol polyphosphate multikinase (IPMK) was first identified as a subunit of the arginine-responsive transcription complex in budding yeast. In addition to its role in the production of inositol tetrakis- and pentakisphosphates ($IP_4$ and $IP_5$), IPMK also exhibits phosphatidylinositol 3-kinase (PI3-kinase) activity. Through its PI3-kinase activity, IPMK activates Akt/PKB and its downstream signaling pathways. IPMK also regulates several protein targets non-catalytically via protein-protein interactions. These non-catalytic targets include cytosolic signaling factors and transcription factors in the nucleus. In this review, we highlight the many known functions of mammalian IPMK in controlling cellular signaling networks and discuss future challenges related to clarifying the unknown roles IPMK plays in physiology and disease.

• Journal of Life Science
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• v.27 no.1
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• pp.8-14
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• 2017

Died Gardenia jasminoides fruit is used as a dye in the food and clothes industries in Asia. The present study investigated the anti-inflammatory effects of aqueous extract of G. jasminoides fruits (GJ) in BV-2 microglial cells. GJ inhibited lipopolysaccharide-induced nitric oxide (NO) secretion, inducible nitric oxide synthase (iNOS) expression, and reactive oxygen species production, without affecting cell viability. Furthermore, GJ increased the expression of heme oxygenase-1 (HO-1) in a dose-dependent manner. Moreover, the inhibitory effect of GJ on iNOS expression was abrogated by small interfering RNA-mediated knock-down of HO-1. In addition, GJ induced nuclear translocation of nuclear factor E2-related factor 2 (Nrf2), a transcription factor that regulates HO-1 expression. GJ-mediated expression of HO-1 was suppressed by LY294002, a phosphoinositide 3-kinase (PI-3K) inhibitor, and SB203580, a p38 kinase inhibitor, but not by the extracellular signal-regulated kinase (ERK) inhibitor PD98059 or c-Jun N-terminal kinase (JNK) inhibitor SP600125. GJ also enhanced the phosphorylation of Akt and p38. These results suggest that GJ suppresses the production of NO, a pro-inflammatory mediator, by inducing HO-1 expression via PI-3K/Akt/p38 signaling. These findings illustrate a novel molecular mechanism by which extract from G. jasminoides fruits inhibits neuroinflammation.

• Proceedings of the PSK Conference
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• 2002.10a
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• pp.241.3-242
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• 2002

Expression of phase II detoxifying genes is regulated by NF-E2-related factor 2 (Nrf2)-mediated antioxidant response element (ARE) activation. Phosphatidylinositol 3-kinase (PI3-kinase) plays an essential role in ARE-mediated rGSTA2 induction by oxidative stress and controls microfilaments and translocation of actin-associated proteins. This study was designed to investigate the P13-kinase-mediated nuclear translocation of Nrf2 and the interaction of Nrf2 with actin. (omitted)